Engraving stylus



Nov. 6, 1956 Percen'r Area Removed J. A. BOYAJEAN 2,769,199

ENGRAVING STYLUS Filed July 1, 1952 0 25 50 f5 I00 Block Whiie I Percen? Penetration INVENTOR.

F|G.3 JOHN A. BOYAJEAN ATTOR N EY United States Patent ENGRAVIN G STYLUS John A. Boyajean, Huntington, N. Y., assignor to Fairchild Camera and Instrument Corporation, a corporation of Delaware Application July 1, 1952, Serial No. 296,593 7 Claims. (Cl. 18-1) This invention relates to engraving styli and, while it is of general application, it is particularly suitable for embodiment in styli for engraving thermally deformable image-reproducing plates by apparatus of the type described and claimed in applicants prior Patent No. 2,575,546.

in the engraving of image-reproducing plates by apparatus of the general type described in aforesaid Patent No. 2,575,546, it is usually proposed to employ an engraving stylus having a pyramidal or conical deforming point. While such styli are entirely satisfactory for many applications, the plate engraved thereby has certain characteristics which are not ideal for some applications. For example, the surface area removed from the plate during engraving is a continuous function of the depth of penetration of the stylus. In the highlight area of the image to be reproduced, the printing areas are in the form of very small islands or plateaus. When printing on rough papers, such as newsprint, or when using relatively viscous inks with poor drying properties, the ink has a tendency to spill over onto the sloping sides of the printing islands and enlarge the actual printing areas thereof, resulting in a tonal distortion. Conversely, in very dark areas of the image, the ink may completely fill the small pits formed by the stylus, again resulting in distortion. These effects introduce a tonal non-linearity into the resulting reproduced image which may act cumulatively with the non-linear characteristics of other imagetranslating or transducing elements of the complete image-reproducing system.

Further, in the ease of plates used for pressing stereotype mats and formed by a conical or a pyramidal stylus, the sloping sides of the printing areas undesirably impede the fiow of the mat material during pressing to form sharply defined printing surfaces on the resulting typemetal casting.

It is an object of the present invention, therefore, to provide a new and improved engraving stylus which obviates one or more of the foregoing limitations on prior engraving styli.

it is another object of the invention to provide a new and improved engraving stylus which is effective to deform a plate in such a manner as to impart thereto an image having a predetermined number of discrete tonal gradations.

It is another object of the invention to provide a new and improved engraving stylus effective to deform a plate to impart thereto a predetermined desired nonlinear penetration-deformed area characteristic.

In accordance with the invention, a stylus for engraving a half-tone plate for image reproduction comprises a metallic shaft terminating in a deforming tip consisting of a series of coaxial steps effective to impart to a plate engraved. thereby a predetermined number of discrete tone gradations.

Further in accordance with the invention, a stylus for engraving a half-tone plate for image reproduction comprises a metallic shaft terminating in a deforming tip, an

axial cross section through the tip having an outline of non-lenear configuration effective to impart a non-linear penetration-deformed area characteristic to a plate engraved by the stylus.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, while its scope will be pointed out in the appended claims.

Referring now to the drawing, Fig. 1 is a perspective view of a stepped engraving stylus embodying one form of the invention;

Fig. 2 is a pernpective view of an engraving stylus embodying another foim of the invention;

Fig. 3 is a graph representing the penetration-deformed area characteristics of the styli of Figs. 1 and 2.

Referring now to Fig. l of the drawing, there is illustrated a heatable stylus 10 for engraving a plate of thermally deformable material, as by the use of the machine of aforesaid Patent No. 2,575,546. The stylus 10 comprises a metallic shaft 10a terminating in a deforming tip consisting of a series of substantially equal coaxial steps 10b, 10c, 10d, and 10e each of a polygonal, specifically a square, cross section. The use of such a stylus is effective to impart to a plate engraved thereby a predetermined number of discrete tonal gradations which is desirable in certain applications where the number of tone steps in limited, for example, in the case of engraving plates for newspaper work. At the same time, the vertical edges of the steps impart to the deformations of an engraved plate similar vertical edges which avoid spilling over of the ink onto the sloping faces of the deformations, as in the case of engraved plates formed by convention styli.

Fig. 2 illustrates a modified form of the invention in which a stylus 11 comprises a shaft 11a terminating in a deforming tip comprising a series of coaxial steps 11b, 11c, 11d, 116, and 11] of circular cross section. In this embodiment of the invention, the steps have unequal incremental dimensions which are so proportioned that an axial cross section through the steps has a mean outline 12 of non-linear configuration. This non-linear configuration of the deforming tip is effective to impart a non-linear or corrective penetration-deformed area characteristic to a plate engraved by the stylus, that is, one in which the gamma is altered or corrected over the brightness range of the reproduced image. By properly proportioning the incremental steps, any desired gamma characteristic may be obtained.

The penetration-deformed area characteristics of the styli of Figs. 1 and 2 are represented by Curves A and B, respectively, of Fig. 3 in which Curve C represents the corresponding characteristic of a conventional pyramidal stylus. Curve D represents the envelope of Curve B or the characteristic corresponding to the mean outline 12 of the stylus of Fig. 2. it will be noted that the styli 10 and 11 are effective to impart to a plate engraved thereby a number of discrete tonal gradations, while the stylus 11 is effective to impart to an engraved plate any desired non-linear or corrective characteristic over each portion of the brightness range in order to compensate for distortion or non-linearity in other portions of the system over corresponding portions of the brightness range.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is: g

1. A stylus for engraving a half-tone plate for image reproduction comprising: ametallic shaft terminating in a deforming tip consisting of a series of coaxial steps, an axial cross section through said steps having a mean outline of non-linear configuration effective to impart a non-linear penetration-deformed area characteristic to a plate engraved by the stylus.

2. A stylus for engraving a half-tone plate for image reproduction comprising: a metallic shaft terminating in a deforming tip consisting of a series of coaxial steps effective to impart to a plate engraved thereby a pre determined number of discrete tone gradations.

3. A stylus for engraving a half-tone plate for image reproduction comprising: a metallic shaft terminating in a deforming tip consisting of a series of coaxial steps of polygonal cross section effective to impart to a plate engraved thereby a predetermined number of discrete tone gradations.

4. A stylus for engraving a half-tone plate for image reproduction comprising: a metallic shaft terminating in a deforming tip consisting of a series of coaxial steps of square cross section effective to impart to a plate engraved thereby a predetermined number of discrete tone gradations.

5. A stylus for engraving a half-tone plate for image reproduction comprising: a metallic shaft terminating in a deforming tip consisting of a series of coaxial steps of circular cross section effective to impart to a plate engraved thereby a predetermined number of discrete tone gradations.

6. A stylus for engraving a half-tone plate for image reproduction comprising: a metallic shaft terminating in a deforming tip consisting of a series of substantially equal coaxial steps effective to impart to a plate engraved thereby a predetermined number of discrete tone gradations.

7. A stylus for engraving a half-tone plate for image reproduction comprising: a metallic shaft terminating in a deforming tip consisting of a series of coaxial steps effective to impart to a plate engraved thereby a predetermined number of discrete tone gradations, said steps having unequal incremental dimensions proportioned to impart a non-linear penetration-deformed area characteristic to a plate engraved by the stylus.

References Cited in the file of this patent UNITED STATES PATENTS 1,747,773 Hedly Feb. 8, 1930 1,914,258 Howey June 13, 1933 2,063,614 McFarlane et al. Dec. 8, 1936 2,213,797 Claussner Sept. 3, 1940 2,238,601 Reynolds Apr. 15, 1941 2,420,614 Norman May 13, 1947 2,442,022 Schulz May 25, 1948 

